Apparatus for making slip castings



Oct. 5, 1943. R A, SHAEFER 2,331,000

m APPARATUS Fon MAKING SLIP CASTINGS Filed Deo. 1s, 1940 /2J'M i /za Patented Get., 5, 1943 animo,

APPARATUS Foa MAKING sur CASTINGS Reinhold A. Shaefer, Rocky Hill, Conn., assigner to Hartford-Empire Company, Hartford, Conn., a corporation of Delaware Application December 18, 1940, Serial No. 376,701

6 Claims. (Cl. 25-129) This invention relates to the manufacture of slip' castings and more particularly to the production by a slip cast process of refractory tubes', feeder spouts and other refractory articles that are suitable for use in contact with molten glass in a glass feeder or for similar service.

In producing a refractory article of the character described by the slip cast process, it 'is usual to pour a suitably prepared slip made of suitable materials into a suitable space surround ing a plaster core in a plaster mold. After the plaster core and mold have absorbed liquid from the slip and the residual casting has dried in the mold for a suficienttime, the core must be removed from such casting. However. the close contact of the casting with the core makes this diillcult of satisfactory accomplishment. In actual practice, the core may be broken and/or the casting damaged by the operations required to separate and remove the core from the tube casting.

An objecty of the present invention is to 0bviate the difficulties previously encountered, as above described, in separating and removing a plaster core from a refractory slip casting surrounding that core in a plaster mold. The present invention attains the above and other objects by providing and making use of a novel combination of structural elements comprising a relatively simple and conveniently'usable mold unit having means for producing a refractory slip casting therein and for separating and displacing the core from the casting 'without likelihood of breaking the core or the mold or damaging the casting.

A further object of the invention is to provide a novel method of effecting release of the slip casting surrounding the plasterfcore in the mold from such core whenthe casting has dried to the extent desired. The present invention also provides a novel method of displacing the core from the casting.

Other objects and advantages of the present invention hereinafter will be described or will become 'apparent from the following description of a practical embodiment of the invention and of its use in the production of a refractory tube casting. Such a practical embodiment of the invention is illustrated in the accompanying drawing by way of example and not of limitation. In the drawing:

The view is a vertical section through a mold unit provided according to the present invention, a portion of a central pressure uid supply pipe of the core of the unit being shown inelevation.

In the drawing, a mold made of a suitable material that will absorb moisture, such as plaster of Paris, is designated l. A core 2 may be made of a similar material and is of suitable size and configuration to be disposed centrally within the mold I so that a .space 3 of suitable size and shape for the casting to 'be made remains between the core and the mold. In the example shown, the casting to be formed is to be cylindrical with an external flange or externally enlarged upper end portion and the space 3 hence is appropriately formed to define a casting oi that description.

The core 2 rests at its bottom on the bottom of the mold I so that the space 3 is closed at its lower end by a portion of the bottom of the mold I. The mold unit includes a mold top 4 which may be made of the same material as the -core 2 and the mold I and is of suitable external size and coniiguration .to be substantially aligned peripherally with the mold I when the mold top is properly located upon the upper end of such mold. The mold top 4 may be provided with vertical apertures 5 for the reception of removable metallic funnels 6 which will then be suitably located to dispose the open lower ends of these funnels'over the annular space 3 at a plurality of places which are spaced angularly around the axis of the mold.

A suitably prepared slip of suitable materials may be poured through the tunnels 8 into the space 3 until the entire annular space l is illled and additlonal'slip is provided in the tunnels to feed material to the underneath casting body as it dries and shrinks and loses liquid to the absorbent plaster core and plaster mold. After the slip casting, indicated at 1 in the drawing, has partially set and dried, the core of the mold unit must be removed. At this time, excess slip may remain in the funnels, as at 8. Features of the invention which obviate diiicultles previously encountered in removing such a core Will now be, pointed out with reference to the particular structure shown in the drawing. I

The core 2, instead of being solid throughout a transverse section thereof, is provided withan axial pressure uid conducting passage 9, shown as the bore of a metallic tube III about which the body of the core 2 has been molded or otherwise formed. The metallic tube I0 is provided at the opposite end portions of the core with encircling annular metallic heads II and I2, respectively, each of which is partially embedded in that end portion of the core so that a portion thereof, designated lla for the head il and I2a for the head I2 projects beyond the adjacent end of the core. As shown, the heads il and 'I2 have identical projecting end portions ila and I2a, each being circular in cross-sectional configuration and tapering slightly toward its outer end.

Each of the heads II and I2 is shown as having an annular groove or channel Hb or I2b in v its periphery into which the material of the core extends so that the head is secured firmly in place in its end portion of the core. The head I2 also is shown as being secured to the tube I0 by a cross pin` I3 and a similar pin may be employed to fasten the head Il to the tube In if de-V outer ends in the body of the core 2 at a suitable v radial distance from the external surface of the core 2. In the example shown, the distance from the outer end of each lateral tube I4 to the outer surface of the core is slightly more than the length -of the lateral tube but this ratio may be varied to a substantial extent in either direction.

The bottom of the mold I has its central portion apertured for the reception of a suitably shaped socket member I5, which may be formed of metal and which is embedded in the bottom wall of the mold I so that the open upper end of the socket I5 is substantially flush with the upper surface of the bottom wall of the mold and is adapted to receive the projecting end porv tion I2a of the head I2 when the core 2 is lowered into the mold I centrally of the latter. The projecting portion I2a of the head I2 has a close telescopic fit with the upper portion of the downwardly tapering socket member I5 when the core is lowered to the bottom of the mold I, leaving a space at I5 between the inserted end portion of the head I2 and the bottom wall |5a, of the socket I5. The telescopic sliding engagement of the projecting portion I2a of the head I2 at the lower end of the core 2 with the downwardly sloping annular side wall of the socket I5 serves to center the core 2 in the mold I when the core is lowered to position in such mold. These parts also may perform a further function according to the present invention, as presently will be pointed out.

The mold top 4 also may be centrally apertured, as at I6, to afford clearance for the upwardly projecting portion of the tube I0. A metallic open ended socket member I'I having an upwardly tapering annular body portion substantially like that of the socket member I 5 may be provided in the apertured central portion of the mold top 4 to telescopically t and engage with the upwardly projecting end portion. IIa of the head member II at the top of the core so as to center the mold top 4 on the mold as such top member is lowered to place on such mold.

A suitable reduction nipple or nozzle I8 may be provided at the lower end of the tube I0 within the socket I5. The upper end of the tube i0 -may be adapted, as by the internal screw threads indicated at I9, for connection with any suitable source of compressed air or fluid under pressure. l

In producing a slip cast refractory tube according to the present invention by the use of the structure described, operations may be performed substantially as follows. At a suitable time, the funneis may moved, the mold top 4 removed from the mold and any surplus material at the top of the casting removed and the top surface of the casting 7 smoothed oi'. The next step is to effect release of the core from the tube casting and to remove such core. In accomplishing this, air under pressure may be supplied to the tube IG. This air will pass outwardly through the lateral outlets from the tube IU and through the pores of the plaster core to the casting 'I. Moisture will be forced from the pores of the plaster core ahead of the air and will form a thin lm of liquid and/or air between the core and the casting I as the latter is forced outwardly from the core by the pressure fluid. This film will aid in effecting clean separation of these parts and will lubricate them so that the core may be readily withdrawn from the casting withoutrequiring the usual hammer blows to drive it from place and without damage to the core or casting.

Air under pressure also may be discharged into the space in the socket I5 to cause the latter to function as a power cylinder. The pressure of the air therein will act on the head I2 as on a piston and will.force such head and the core upward and thus aid removal or withdrawal of the core from the casting. The pressure on the air may be selected to meet the requirements of each particular operation. Air under a pressure of approximately 15 lbs. and applied but for a brief period. has been satisfactorily employed in practice. n

If desired, the mold unit may be inverted during the step of removing the core from the casting for convenience of operation or for any other useful purpose. It of course will be understood that the shrinkage of the casting will be away from the side wall of the outer mold I so that ordinarily there is no diculty in removing a slip casting from such a mold.

By the use of the present invention, the same core may be used repeatedly in the production of successive similar castings. The casting will be undamaged by the removal of the core and hence may be made of slips which in turn are made of the materials best adapted for the production of refractory tubes most suitable for the service intended. Moreover, the operation of producing the tube casting may be carried on without the necessity of accepting less than the most suitable time periods involved and consequently the slip casting may be dried adequately on the core for the most desirable results in the manufacture of the final tube.

The invention is not restricted to the particular structure shown and described or to use for the production of this type of casting alone but may embody suitable apparatus for producing slip castings of various configurations and intended for various uses.

I claim:

1. Apparatus for making slip cast refractory tubes comprising an upright substantially cylindrical mold open at its upper end, a substantially cylindrical core disposed within said mold in spaced concentric` relation therewith so as to leave an annular space between the core and thc inner side wall of the mold, a metallic tube extending axially through the core, said tube being open at its upper end fon the entry of air under pressure thereinto and having an outlet at its centered position within said hollow mold when lower end for discharge of air under pressure therefrom, an open-topped socket member at the bottom of the mold beneath the lower end of said core and in position to receive air under pressure from said metallic tube, said socket member being closed at its bottom, and an annular head surrounding the lower end of the metallic tube and having a portion projecting beneath the bottom of the core for engaging slidably with said open-topped socket member at the bottom of the mold to aid in centering the core in the mold and to serve as a piston for moving the core upward under the pressure of air supplied through said metallic tube to the underlying space in said open-topped socket member.

2. Apparatus for making slip cast refractory tubes comprising an upright open-topped substantially cylindrical mold, a substantially cylindrical core disposed withinthe mold in spaced concentric relation therewith so as to leave an annular space between the core and the inner side wall of the mold for the reception of a slip to form a tube casting, said core being made of a material that will absorb moisture from the slip, and a pneumatic device for impelling the core upwardly relatively to the tube casting, said pneumatic device comprising an open-topped socket member in the bottom portion of the mold` beneath the core, said socket member being closed at its bottom, a piston carried by the core at its bottom for entering and forming a substantially the core is lowered axially in the mold to the botair-tight sliding contact with-the'internal side.

walls of said socket member, and means for supplying airunder pressure to said socket member.

va material that will absorb moisture from the slip, and a pneumatic devicel for impelllng the core upwardly relatively to the tube casting, said pneumatic device comprising an open-topped socket member in the bottom portion of the mold beneath the core, said socket member being closed at its bottom, a piston carried by the core at its bottom for entering and forming a substantially air-tightsliding contact with the internal side walls of said socketmember, and means for supplying air under pressure to said socket member g and for forcing air under pressure outwardly from an axial portion of the corethrough the pores thereof against said tube casting.

4. Apparatus for making refractory slip castings comprising an upright hollow mold openat its top and having a bottom, a substantially cylindrical core movable axially through the open' upper end of said hollow mold to and from position to rest at its lower end upon the bottom of said hollow mold, the diameter of said core being substantially less than the inner diameter of said hollow mold, cooperative core centering members respectively carried by the lower end portion of the core and the bottom of the hollow mold and having tapering portions telesoopically engaging each other to guide the lower -end` of the core to a tom thereof in approximately concentric relation with said mold, leaving an annular space between said core and the inner side wall of the mold, a mold top fitting upon said hollow mold and an open funnel extending vertically through a portion of the mold top in position to discharge the materials oi a suitably prepared slip downwardly into the annular space within the mold around the -core therein when said mold top is in operative position upon the mold.

5. Apparatus for making refractory slip castings comprising an upright hollow mold open at its top and having a bottom, a substantially cylindrical core movable axially through the open upper end of said hollow mold to and from position to rest at its lower end upon the bottom of said hollow mold, the diameter of said core being substantially less than the inner diameter of said hollow mold', cooperative core centering members respectively'carried by the lower end portion of the core and the bottom of the hollow mold and having tapering portions telescopically engaging each other to guide the lower end ot the core to a centered position within said hollow mold when the core is lowered axially in the mold to the bottom thereof in approximately concentric relation with said mold, leaving an annular space between said core and the inner side wall of the mold, a mold top tting upon said hollow mold and cooperative 'core centering members respectively carried by the upper end portion of the corewithin the mold and by said mold'top `and having tapering portions telescopically engaging each other to guide the upper end portion of the core to a centered position within the mold whenthe mold top is placed lin its said operative position upon the mold.

6. Apparatus for making refractory slip castings of tubular form comprising an upright hollow mold open at its top and having a bottom. a substantially cylindrical core resting at its lower l end upon the bottom of said hollow mold in apthe latter, said tube being formed at its upperv end for connection with a source of air under pressure and being provided at numerous places throughout the length of the portion thereof that is located within said core with lateral outlets for the discharge of air from the interior of the tube outwardly through the material composing the core toward the space-between said core and the inner wall or said-hollow mold, certain of said lateral outlets being located diametrically opposite other of said lateral outlets so as to provide a plurality of pairs of diametrically opposite 

